Sleep-disordered breathing (SDB) affects at least 1 to 3% of children. Associated morbidity can include inattentive and hyperactive behavior, disruptive behavior disorders, cognitive deficits, and excessive daytime sleepiness. Sleep specialists recommend that children undergo polysomnography to confirm SDB, especially before adenotonsillectomy, which is the most common treatment. However, otolaryngologists rarely obtain such testing either before or after surgery. Published reports show that a clinical diagnosis of SDB does not predict polysomnographic results reliably, but the extent to which bolysomnographic measures themselves predict morbidity, and especially treatable morbidity, is not well known. Preliminary data from the investigators suggest that standard SDB measures, such as rates of apneas and hypopneas, rates of arousals from sleep, and the extent of oxygen desaturation, do not reliably predict neurobehavioral morbidity or its improvement. In contrast, two newer techniques, rarely used in clinical practice, do show unique predictive value. The first is an innovative signal processing algorithm developed and validated by thfe investigators to assess the extent to which cortical EEC activity changes in synchrony with non-apneic respiratory cycles in children with SDB. The second, esophageal pressure monitoring, is a gold-standard measure of the increased respiratory effort that characterizes SDB. The main goal of this revised competitive renewal application, therefore, is to study and improve methods for identification of childhood SDB that carries reversible morbidity. The investigators will administer nocturnal polysomnography and well-validated assessments of behavior, psychiatric status, cognition, and sleepiness to 100 children scheduled for clinically-indipated adenotonsillectomy, and to 50 matched control subjects. All evaluations will be repeated 6 months later to complete this controlled, non-randomized follow-up trial. Specific Aim 1 is to determine whether pre-operative respiratory cycle-related EEC changes (RCREC), rather than standard polysomnographic arousals, can predict neurobehavioral morbidity and its improvement after surgery. Aim 2 is to assess whether esophageal pressure', rather than standard SDB measures, can predict the same outcomes. Aim 3 is to evaluate the post-operative utility of the newer and standard measures in identification of clinically-relevant residual SDB. This investigation of two fundamental SDB characteristics -increased respiratory effort arid its correlation with cortical identification of childhood SDB and risk for neurobehavioral impact activity - may well lead to fundamental improvement in identification of childhood SDB and risk for neurobehavioral impact.